CODEWITHSUNDEEP
mysqlruby-on-railsmigration
Mark Robinson
Mark Robinson

Reputation: 1619

Combining data from 2 Rails apps?

I have 2 Rails apps with the same models apart from a couple of attributes. I now need to merge these apps and I'm trying to work out how to merge their data. The challenges are:

I'm aware of seed_dump and yaml_db but I'm not sure they're a good solution for my problem

Upvotes: 1

Views: 155

Answers (1)

R. Sierra
R. Sierra

Reputation: 1204

I faced a similar situation some time ago, with an app designed with database multitenancy. To merge all data into a single database I ended up creating a rake task, that would go through every record and association and recreate them in the new database.

The task had two arguments SOURCE and DESTINATION, and it would be run like: rake db:merge SOURCE=some_database DESTINATION=new_database. The task was run for each database I needed to merge.

Inside the rake task the idea was something like this:

namespace :db do
  task :merge => [:environment, :load_config] do |t, args|
  raise "Empty SOURCE provided" if not ENV["SOURCE"] or ENV["SOURCE"].empty?
  @source = ENV['SOURCE'].to_sym
  @destination = (ENV['RAILS_ENV'] || 'development').to_sym

  # for each model
  ActiveRecord::Base.establish_connection(@source)
  # obtain the records and its associations
  ActiveRecord::Base.establish_connection(@destination)
  # loop through each record and build all associated records
  # apply any necesary transformation to data
  # then build the record and fill it with the new associations
  # skip callbacks / validations if needed
  # then save

In some cases to keep track of ids in associations I used hashes, that tracked the original and new id.

I know the complexities of each app can make this process really hard, but in my case this idea resulted to be very usefull as a starting point.

Upvotes: 1

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